1. Field of the Invention
The present invention relates to a light-emitting device.
2. Description of the Related Art
FIG. 15A is a schematic drawing showing an arrangement of components in a general light-emitting diode (LED) disclosed in, for example, Japanese Utility Model Registration No. 3068914 and FIG. 15B is a schematic sectional view taken along line B-B in FIG. 15A. As shown in FIGS. 15A and 15B, the light-emitting diode includes a substrate 110A made of, for example, sapphire, an underlying layer 110B formed by, for example, a MOCVD method (Metal-Organic Chemical Vapor Deposition) method, and a luminescent layer formed on the substrate 110A and having a laminated structure in which a first compound semiconductor layer 111 of a first conductivity type (e.g., n type), an active layer 112 having a quantum well structure, and a second compound semiconductor layer 113 of a second conductivity type (e.g., p type) are laminated. Also a second electrode (p-side electrode) 122 is provided on the second compound semiconductor layer 113. Further, the second compound semiconductor layer 113 and the active layer 112 are partially removed to expose a portion of the first compound semiconductor layer 111, and a first electrode (n-side electrode) 121 is provided on the exposed portion of the first compound semiconductor layer 111. A current flows from the second electrode (p-side electrode) 122 to the first compound semiconductor layer 111 and the first electrode 121 (n-side electrode) through the active layer 111 provided immediately below the remaining portion of the second compound semiconductor layer 113. As a result, in the active layer 112, the quantum well structure is excited by injection of the current to cause a luminescent state over the entire surface.
In a light-emitting diode of a type in which light is emitted from the substrate side, light from the active layer 112 is emitted directly to the outside through the substrate 110A or reflected by the second electrode 122 and then emitted to the outside through the substrate 110A. As a material for forming the second electrode 122, for example, silver (Ag) having high reflectance is used. In order to improve the reliability of the second electrode 122, the second electrode 122 is generally covered with an insulating film 114 by a CVD method such as plasma CVD or a PVD method such as vacuum deposition or sputtering. The insulating film 114 has openings 123 and 124 provided above the first and second electrodes 121 and 122, respectively, and first and second pads 125 and 126 are provided on the exposed portions of the first and second electrodes 121 and 122, respectively.
Another light-emitting device known from Japanese Unexamined Patent Application Publication No. 2006-19347 includes a semiconductor light emitting element having n and p electrodes provided on a plane and a mount member for flip-chip connecting the semiconductor light-emitting element, the n electrodes of the semiconductor light emitting elements being formed at the vertexes of a substantially regular triangle, and the p-electrode being formed to surround at least one n electrode.